Goldman Sachs Puts Coal In Black Friday's Stocking

Retail sales were strong for this Black Friday weekend, but Goldman Sachs analyst Adrianne Shapira raises red flags for what was an “encouraging start” for this holiday’s shopping season.

“What we’ve been seeing is a pretty consistent theme, that the cost of doing business or the cost of getting the customer’s attention is going up and that usually does not bode well for margins” Shapira told CNBC.

The cost she is referring to is the increase in free online shipping, sharper deals, intensified marketing and earlier store opening hours seen across many retailers, which have really driven sales volumes and foot traffic this weekend.

According to Shapira, Wal-Mart's playbook has always been about being a price leader, and the mass retailer was the big winner this Black Friday weekend, reclaiming that title.

But it may be at a cost.

“We believe the company did reclaim lost share, but at the expense of margin for them and others. On the cover of the Wal-Mart circular, their prices were down 14 percent year-over-year versus an average 27 percent increase.”

The National Retail Federation estimates an increase of 6 percent in shopping volume this weekend from a year ago. Shapira says it was all about “go early or go home” this year, which seemed successful in driving sales. But it may be too early to gauge if early openings proved to be incremental or pull forward sales.

“Everything seems to have been shifted a little bit earlier" and there's a "lot of business still to be done,” she said. The question is whether that "translates into profitability" for retailers because "I think it is coming a bit at the expense of margins."